(a) Field of the Invention
This invention generally relates to a system and method for capturing ferrous objects that are being carried by a flow of material, such as a flow of food waste along a trough. More particularly, but not by way of limitation, to system that and method that uses static focused magnets to pull and retain ferrous items, such as silverware, at a location over the flow of food waste.
(b) Discussion of Known Art
In the food service industry it is common practice to clean and sanitize a large number of dishes or trays that contain waste food scraps in a short period of time. To achieve this task, common practice in the industry provides for an assembly line type of arrangement, where trays or dishes are first cleared of waste food materials and then placed on conveyors or carrying racks that transport the dishes, flatware, and trays, into a large capacity washing installation.
The waste food products removed from the dishes or trays are collected in a trough or duct that is used to carry these waste products to a device, such as a grinder or disposer, that grinds the waste materials, so that it may then be easily washed into the sewage system of the restaurant, cafeteria, or other food service institution. The grinding or disposal equipment used in these applications is designed for grinding relatively soft material, and, consequently, is vulnerable to serious damage in the event that flatware, or other items that include ferrous components, falls into the grinding equipment.
It is well known that magnets may be used to pull ferrous items from the flow of waste food being delivered to the grinder or disposer. For example U.S. Pat. No. 4,706,818 to Zutell et al. teaches a magnetic system that is installed along the flow path of the waste products in order to ensure contact of the magnets used with the system and flatware that is being carried in the waste materials being carried into the grinder.
Another example is found in U.S. Pat. No. 3,926,792 to Buford. Buford teaches the placement of magnets behind a conveyor belt to attract ferrous objects being carried on or next to the belt. This solution however is limited in scope. This limited solution is particularly useful in applications that use conveyor belts, but provides little guidance for an application that uses a trough that carries a mixture of water and waste food.
Yet another device that uses magnets to remove metal from waste food products is shown in U.S. Pat. No. 4,744,469 to Swallert. The Swallert system teaches the use of magnets in conveyor type systems, but give little guidance as how to solve the problem of removing ferrous objects, such as flatware, from a flow of material as is found in a trough carrying water and waste material into a grinding device.
Still another device that addresses the removal of flatware form a conveyor system is taught in U.S. Pat. No. 3,486,939 to Pinckard. The Pinckard device, like the Swallert device is particularly useful for removing flatware and other ferrous objects from a conveyor belt, but does little to address the problems associated with removing these types of items from a moving flow of material.
Therefore, a review of known devices reveals that there remains a need for a system that can be used to remove flatware or other ferrous objects from a moving flow of material that is carrying the flatware.
Still further, there remains a need for a system that can be used to modify existing flow based waste carrying systems, without having to modify extensively the existing trough or arrangement used to wash the waste products towards a grinding or disposal system.
It has been discovered that the problems left unanswered by known art can be solved by providing a stationary, focused magnetic field that is focused at a location over the main flow of food waste. In a preferred embodiment, the magnetic field has been focused such that the highest density of magnetic flux is along a direction that is transverse to the flow of food waste, and at a distance away from the flow.
It has been discovered that by providing this focused magnetic flux at a distance over the flow of waste food, one can cause ferrous items such as silverware to be pulled from the flow and suspended by way of the magnetic field along a volume where the magnetic flux is at its highest density. Thus, by focusing the magnetic field so that strongest area of flow is along an area away from the main flow of waste food and generally on a different plane from the flow of waste food.
In a highly preferred embodiment of the invention, the focused magnetic field is generated by providing a magnet assembly that includes at least two magnets separated by a non-magnetic spacer, and joined by a ferrous plate that concentrates and facilitates the magnetic flux from one magnet to the other. The entire assembly is held within an enclosure that allows mounting of the assembly at a desired location relative to the flow of waste food. For example, in an application where the flow of waste food is defined by a trough, and in most institutional applications this trough is made of stainless steel, which is non-magnetic, the enclosures disclosed herein are positioned against the sides of the trough. The enclosures will be positioned such that the focused region of magnetic flux emanating from the enclosure flows along a plane that is generally parallel to the flow of waste food. Most preferably, this flux will be at an angle that lies along a plane that is parallel to the flow of the waste food.
In a highly preferred embodiment, the enclosures are positioned at a location along the trough, on opposite sides of the trough, with the region of concentrated flux lying along a line over the flow of waste food. The presence of the two magnetic fields pulling in opposite directions from one another ensures that ferrous items, such as silverware, is pulled from the flow of waste food and suspended over the flow of waste food in an orientation that is generally aligned with the line or axis extending between the two enclosures.
It should also be understood that while the above and other advantages and results of the present invention will become apparent to those skilled in the art from the following detailed description and accompanying drawings, showing the contemplated novel construction, combinations and elements as herein described, and more particularly defined by the appended claims, it should be clearly understood that changes in the precise embodiments of the herein disclosed invention are meant to be included within the scope of the claims, except insofar as they may be precluded by the prior art.